Our objective is to explore selected problems in reproduction from the molecular, i.e., biochemical viewpoint. The rabbit will be used to evaluate contraceptive systems based on inhibition of acrosomal enzymes essential for fertilization. The nature of corona penetrating enzyme, its substrate and its inhibition will be investigated. The role of proteolysis in follicle rupture, the composition of the zona pellucida and the block to polyspermy as initiated by cortical granule material will be investigated.